Juve have taken disciplinary action against the wantaway Brazil midfielder after he skipped the first day of preseason training.
With Luiz pushing to be sold, Capello told La Gazzetta dello Sport: "It's a shame, because I think he's underrated. He's on the list of departures and hasn't been convincing, but I liked him even though he then disappeared.
"I thought he had the necessary quality, that he was a good player. He's one of those players who now don't consider themselves good, but perhaps they haven't been given the conditions to perform at their best. Even Nico Gonzalez, for example. But let's take a step back."
Capello also said, "Juventus spent a lot of money last year, they had signed players they had considered from Juventus: especially Nico, Douglas and (Teun) Koopmeiners. Well, it seems impossible to see the latter in such difficulty after what he did at Atalanta.
"They are all players who probably have not managed to integrate and give what was expected: we have to ask ourselves some questions, now the risk is that some of them go to another team and become what they were not at Juventus."